pdf_interpret/

util.rs

//! A number of utility methods.

use kurbo::{Affine, BezPath, PathEl, Rect};
use log::warn;
use pdf_syntax::page::{Page, Rotation};
use siphasher::sip128::{Hasher128, SipHasher13};
use std::hash::Hash;
use std::ops::Sub;

pub(crate) trait OptionLog {
    fn warn_none(self, f: &str) -> Self;
}

impl<T> OptionLog for Option<T> {
    #[inline]
    fn warn_none(self, f: &str) -> Self {
        self.or_else(|| {
            warn!("{f}");

            None
        })
    }
}

const SCALAR_NEARLY_ZERO: f32 = 1.0 / (1 << 8) as f32;

/// A number of useful methods for f32 numbers.
pub trait Float32Ext: Sized + Sub<f32, Output = f32> + Copy + PartialOrd<f32> {
    /// Whether the number is approximately 0.
    fn is_nearly_zero(&self) -> bool {
        self.is_nearly_zero_within_tolerance(SCALAR_NEARLY_ZERO)
    }

    /// Whether the number is nearly equal to another number.
    fn is_nearly_equal(&self, other: f32) -> bool {
        (*self - other).is_nearly_zero()
    }

    /// Whether the number is nearly equal to another number.
    fn is_nearly_less_or_equal(&self, other: f32) -> bool {
        (*self - other).is_nearly_zero() || *self < other
    }

    /// Whether the number is nearly equal to another number.
    fn is_nearly_greater_or_equal(&self, other: f32) -> bool {
        (*self - other).is_nearly_zero() || *self > other
    }

    /// Whether the number is approximately 0, with a given tolerance.
    fn is_nearly_zero_within_tolerance(&self, tolerance: f32) -> bool;
}

impl Float32Ext for f32 {
    fn is_nearly_zero_within_tolerance(&self, tolerance: f32) -> bool {
        debug_assert!(tolerance >= 0.0, "tolerance must be non-negative");

        self.abs() <= tolerance
    }
}

/// A number of useful methods for f64 numbers.
pub trait Float64Ext: Sized + Sub<f64, Output = f64> + Copy + PartialOrd<f64> {
    /// Whether the number is approximately 0.
    fn is_nearly_zero(&self) -> bool {
        self.is_nearly_zero_within_tolerance(SCALAR_NEARLY_ZERO as f64)
    }

    /// Whether the number is nearly equal to another number.
    fn is_nearly_equal(&self, other: f64) -> bool {
        (*self - other).is_nearly_zero()
    }

    /// Whether the number is nearly equal to another number.
    fn is_nearly_less_or_equal(&self, other: f64) -> bool {
        (*self - other).is_nearly_zero() || *self < other
    }

    /// Whether the number is nearly equal to another number.
    fn is_nearly_greater_or_equal(&self, other: f64) -> bool {
        (*self - other).is_nearly_zero() || *self > other
    }

    /// Whether the number is approximately 0, with a given tolerance.
    fn is_nearly_zero_within_tolerance(&self, tolerance: f64) -> bool;
}

impl Float64Ext for f64 {
    fn is_nearly_zero_within_tolerance(&self, tolerance: f64) -> bool {
        debug_assert!(tolerance >= 0.0, "tolerance must be non-negative");

        self.abs() <= tolerance
    }
}

pub(crate) trait PointExt: Sized {
    fn x(&self) -> f32;
    fn y(&self) -> f32;

    fn nearly_same(&self, other: Self) -> bool {
        self.x().is_nearly_equal(other.x()) && self.y().is_nearly_equal(other.y())
    }
}

impl PointExt for kurbo::Point {
    fn x(&self) -> f32 {
        self.x as f32
    }

    fn y(&self) -> f32 {
        self.y as f32
    }
}

/// Calculate a 128-bit siphash of a value.
pub(crate) fn hash128<T: Hash + ?Sized>(value: &T) -> u128 {
    let mut state = SipHasher13::new();
    value.hash(&mut state);
    state.finish128().as_u128()
}

pub(crate) trait BezPathExt {
    fn fast_bounding_box(&self) -> Rect;
}

impl BezPathExt for BezPath {
    fn fast_bounding_box(&self) -> Rect {
        let mut min_x = f64::INFINITY;
        let mut min_y = f64::INFINITY;
        let mut max_x = f64::NEG_INFINITY;
        let mut max_y = f64::NEG_INFINITY;

        let mut include = |x: f64, y: f64| {
            min_x = min_x.min(x);
            min_y = min_y.min(y);
            max_x = max_x.max(x);
            max_y = max_y.max(y);
        };

        for el in self.elements() {
            match *el {
                PathEl::MoveTo(p) | PathEl::LineTo(p) => include(p.x, p.y),
                PathEl::QuadTo(p1, p2) => {
                    include(p1.x, p1.y);
                    include(p2.x, p2.y);
                }
                PathEl::CurveTo(p1, p2, p3) => {
                    include(p1.x, p1.y);
                    include(p2.x, p2.y);
                    include(p3.x, p3.y);
                }
                PathEl::ClosePath => {}
            }
        }

        if min_x > max_x {
            Rect::ZERO
        } else {
            Rect::new(min_x, min_y, max_x, max_y)
        }
    }
}

/// Extension methods for rectangles.
pub trait RectExt {
    /// Convert the rectangle to a `kurbo` rectangle.
    fn to_kurbo(&self) -> Rect;
}

impl RectExt for pdf_syntax::object::Rect {
    fn to_kurbo(&self) -> Rect {
        Rect::new(self.x0, self.y0, self.x1, self.y1)
    }
}

// Note: Keep in sync with `pdf-interpret-write`.
/// Extension methods for PDF pages.
pub trait PageExt {
    /// Return the initial transform that should be applied when rendering. This accounts for a
    /// number of factors, such as the mismatch between PDF's y-up and most renderers' y-down
    /// coordinate system, the rotation of the page and the offset of the crop box.
    fn initial_transform(&self, invert_y: bool) -> Affine;
}

impl PageExt for Page<'_> {
    fn initial_transform(&self, invert_y: bool) -> Affine {
        // Use the raw CropBox origin for the coordinate-system translation.
        // MuPDF maps (CropBox.x0, CropBox.y0) → canvas (0, 0).  For normal
        // PDFs (CropBox ⊆ MediaBox) intersected_crop_box and crop_box share
        // the same origin, so there is no change.  For unusual documents where
        // CropBox extends beyond MediaBox (e.g. gen-802: CropBox=[0,0,684,864]
        // but MediaBox=[36,36,648,828]) the intersected origin was (36,36),
        // producing a 75-pixel content offset vs MuPDF. (#544 follow-up)
        let crop_box = self.crop_box();
        let (_, base_height) = self.base_dimensions();
        let (width, height) = self.render_dimensions();

        let horizontal_t =
            Affine::rotate(90.0_f64.to_radians()) * Affine::translate((0.0, -width as f64));
        let flipped_horizontal_t =
            Affine::translate((0.0, height as f64)) * Affine::rotate(-90.0_f64.to_radians());

        let rotation_transform = match self.rotation() {
            Rotation::None => Affine::IDENTITY,
            Rotation::Horizontal => {
                if invert_y {
                    horizontal_t
                } else {
                    flipped_horizontal_t
                }
            }
            Rotation::Flipped => {
                Affine::scale(-1.0) * Affine::translate((-width as f64, -height as f64))
            }
            Rotation::FlippedHorizontal => {
                if invert_y {
                    flipped_horizontal_t
                } else {
                    horizontal_t
                }
            }
        };

        let inversion_transform = if invert_y {
            Affine::new([1.0, 0.0, 0.0, -1.0, 0.0, base_height as f64])
        } else {
            Affine::IDENTITY
        };

        rotation_transform * inversion_transform * Affine::translate((-crop_box.x0, -crop_box.y0))
    }
}